First cut at Exit Fullscreen bubble on Linux.

chrome/browser/gtk/browser_window_gtk.h

 // Copyright (c) 2009 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_GTK_BROWSER_WINDOW_GTK_H_
 #define CHROME_BROWSER_GTK_BROWSER_WINDOW_GTK_H_
 
 #include <gtk/gtk.h>
 
 #include <map>
@@ skipping 17 matching lines @@
 }
 #endif
 
 class BookmarkBarGtk;
 class Browser;
 class BrowserTitlebar;
 class BrowserToolbarGtk;
 class CustomDrawButton;
 class DownloadShelfGtk;
 class FindBarGtk;
+class FullscreenExitBubbleGtk;
 class InfoBarContainerGtk;
 class LocationBar;
 class StatusBubbleGtk;
 class TabContentsContainerGtk;
 class TabStripGtk;
 
 // An implementation of BrowserWindow for GTK.
 // Cross-platform code will interact with this object when
 // it needs to manipulate the window.
 
@@ skipping 375 matching lines @@
   guint32 last_click_time_;
   gfx::Point last_click_position_;
 
   // If true, maximize the window after we call BrowserWindow::Show for the
   // first time.  This is to work around a compiz bug.
   bool maximize_after_show_;
 
   // The accelerator group used to handle accelerators, owned by this object.
   GtkAccelGroup* accel_group_;
 
+  scoped_ptr<FullscreenExitBubbleGtk> fullscreen_exit_bubble_;
+
   DISALLOW_COPY_AND_ASSIGN(BrowserWindowGtk);
 };
 
 #endif  // CHROME_BROWSER_GTK_BROWSER_WINDOW_GTK_H_